Interference-fringe counter for measuring small lengths

Summary

• 1. For measuring small lengths (1–2 mm) it was found expedient to construct an interferometer with a fringe counter by using standard instruments produced by our industry.

• 2. The mean-square error of such an interferometer does not exceed 0.22μ, which is perfectly satisfactory for the majority of measurements in the engineering industry.

• 3. The interferometer can be easily adapted for measuring micron indicator gages, screws of eyepiece micrometers, for determining coefficients of linear expansion and similar operations.

• 4. For more accurate measurements, the error of the set can be reduced by means of a device which registers fractions of the interference ordinal with an error of 1/2 a fringe.